linux-kernel - [PATCH v4 1/2] x86/cpufeatures: Add AMD FAST CPPC feature flag

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Message-ID: <e717feea3df0a178a9951491040a76c79a00556c.1716649578.git.Xiaojian.Du@amd.com>
Date: Sat, 25 May 2024 23:08:43 +0800
From: Xiaojian Du <Xiaojian.Du@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	<linux-pm@...r.kernel.org>
CC: <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <hpa@...or.com>,
	<daniel.sneddon@...ux.intel.com>, <jpoimboe@...nel.org>,
	<pawan.kumar.gupta@...ux.intel.com>, <sandipan.das@....com>,
	<kai.huang@...el.com>, <ray.huang@....com>, <rafael@...nel.org>,
	<Perry.Yuan@....com>, <gautham.shenoy@....com>, <Borislav.Petkov@....com>,
	<mario.limonciello@....com>, Perry Yuan <perry.yuan@....com>, Xiaojian Du
	<Xiaojian.Du@....com>
Subject: [PATCH v4 1/2] x86/cpufeatures: Add AMD FAST CPPC feature flag

From: Perry Yuan <perry.yuan@....com>

Some AMD Zen 4 processors support a new feature FAST CPPC which
allows for a faster CPPC loop due to internal architectural
enhancements. The goal of this faster loop is higher performance
at the same power consumption.

Reference:
See the page 99 of PPR for AMD Family 19h Model 61h rev.B1, docID 56713

Signed-off-by: Perry Yuan <perry.yuan@....com>
Signed-off-by: Xiaojian Du <Xiaojian.Du@....com>
Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/scattered.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 3c7434329661..6c128d463a14 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -470,6 +470,7 @@
 #define X86_FEATURE_BHI_CTRL		(21*32+ 2) /* "" BHI_DIS_S HW control available */
 #define X86_FEATURE_CLEAR_BHB_HW	(21*32+ 3) /* "" BHI_DIS_S HW control enabled */
 #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
+#define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* "" AMD Fast CPPC */
 
 /*
  * BUG word(s)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index af5aa2c754c2..c84c30188fdf 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -45,6 +45,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_HW_PSTATE,	CPUID_EDX,  7, 0x80000007, 0 },
 	{ X86_FEATURE_CPB,		CPUID_EDX,  9, 0x80000007, 0 },
 	{ X86_FEATURE_PROC_FEEDBACK,    CPUID_EDX, 11, 0x80000007, 0 },
+	{ X86_FEATURE_FAST_CPPC, 	CPUID_EDX, 15, 0x80000007, 0 },
 	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
 	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
 	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },
-- 
2.34.1